10 Reasons Why Some Messages Don't Get Delivered

Phoning a friend? If their phone is turned off, you'll know it right away. But what about a text? You may never know if your message got delivered.

Global messaging using A2P (Application to Person) messaging (or SMS API) platforms is complicated, as most of the heavy lifting is done without you knowing it. Today, we're going to show you the main reasons why SMS text messages go undelivered.

1) The recipient's phone is switched off

If you get a busy signal while calling, you try again later. But when the SMS doesn’t get delivered on the first try, it is automatically re-sent in certain intervals. When the phone is available again, the message gets delivered.

If a certain amount of time passes without the SMS being successfully delivered, your mobile carrier might decide to stop trying. For example, Messente's system is configured to try to deliver messages within 6 hours. If the message still won't go through, it is eventually marked as 'Failed.'

If you do get a 'Failed' warning on one of your messages, then you know that the delivery has definitely not been successful. At this point, you can try and resend the message, and the process will be repeated.

If this reoccurs, then it can be hard to know whether the recipient's phone is switched off, or there is a more serious problem with either your phone or theirs. Most people will have their phones turned on at some point during the day, so if your message goes a whole 24 hours without being delivered, then it's fair to assume that a switched-off phone is not the explanation. 

2) False negative

Sending SMS text messages also requires receiving Delivery Reports (DLR) from carriers or operators. When the operator fails to respond with the correct receipt, the sender isn't notified of the delivery and marks it as 'Failed.'

Unfortunately, there are many cases where the operator has a problem on their end and the DLR is not sent through correctly. The most annoying thing is that the sender will have no idea that this is the issue and instead think that the problem lies elsewhere.

If you're the person trying to send messages, then there's really no way to know if you've run into a false negative. Ultimately, you only know if a message is delivered by receiving a reply.

USA, Canada, and most Latin-American countries are known not to provide delivery reports at all.

3) The number is roaming (abroad)

If you're trying to send SMS messages to a number that is currently not in the home-country often causes problems, and frequently, delivery to numbers that are roaming is not guaranteed. It's also worth noting that sending an SMS abroad can be very expensive, especially if you don't have international messages included in your data plan.

If you know beforehand that the recipient is abroad but you still want the message to get through to them, then there are a few things to remember. Firstly, be sure to use the correct country code, which is inserted before the phone number. Additionally, ensure that your carrier allows international SMS messaging - your messages won't be sent if this is not the case.

If you're a business sending messages to phone numbers all around the world, then you should check that you are collecting your clients' country codes when they share their numbers with you.

4) The sender you are using is prohibited

Some countries or operators are blocking some types of senders or A2P messaging platforms. Japan, for example, doesn’t allow sending A2P SMS messages from regular phone numbers. 

These restrictions are put in place to prevent companies from engaging in high-volume messaging or spam. In these cases, it's more difficult to run A2P marketing strategies, even if you're not going to be spamming your clients.

Make sure to do your research around the rules and laws in your country. As long as you understand what is and isn't allowed, you shouldn't have any problems running a successful marketing campaign with an A2P strategy.

5) The carrier is blocking the SMS

Operators are also known to block some SMS routes from time to time. This also requires SMS services to re-route the message via another working route, which can cause temporary delivery issues. These problems are usually resolved quickly, but they can slow down your message delivery quite significantly.

Keep an eye out for any service updates from your provider since they will usually let you know when they're experiencing problems. In the meantime, it might be worth holding back on sending too many messages that won't be delivered right away.

6) Local regulations restrict SMS text messages

In some countries, local regulations restrict sending SMS messages to prevent spam. For example in some countries, messages notated as marketing can be sent only during workdays from 8 am to 8:30 pm. Although this can be annoying, it just takes a bit of planning to ensure you're only sending marketing A2P messages in the allowed hours.

If you're sending SMS messages to phone numbers all over the world, then it can get a little complicated to keep track of local restrictions. Luckily, many A2P services will have the capability to automatically send your text messages at specific times - once you've set this up, everything should take care of itself.

7) The number might be in the Do Not Disturb list

In some countries, the operators have a list, where handset owners can add their phone number by themselves so no messages from an A2P connection can be delivered. Ultimately, it's problematic should one need to receive helpful information from a business, such as delivery information and order updates.

Some people might only have local numbers approved to avoid spam texts, so you'll struggle to reach them if you're not in the same country. There's not really much you can do to solve this, aside from prompting your customers to add your A2P number to their "allowed" contacts.

8) The handset settings have "receive SMS messages" turned off

These days, SMS messaging isn't the only way that people receive text messages. Many smartphones have internet-based messaging as their main person-to-person texting medium. Lots of people also use social network messaging apps to get in touch with each other.

As a result of this, it's not uncommon for recipients to have their SMS messages deactivated, and some people might not even know that it's turned off.

Often, there are conflicts between different applications that receive SMS texts, causing applications not to receive messages. If their SMS receiving capability turned off, SMS messages cannot be delivered properly to the phone number.

This issue can be further compounded by a user removing a conflicting app, but not changing SMS message settings to receive.

9) Conflicting SMS applications

Sometimes different applications on the handset can receive SMS messages. Due to their conflicts, the messages are not being delivered as the applications are conflicting and the message is not able to deliver to any of them, resulting in a failed message.

In simple terms, different applications are fighting to receive the same message, but in the end, it doesn't get through to any of them. This is yet another problem that cannot be rectified from the sender's side, and it's down to the recipient to alter their receiving messages settings.

The only thing the sender can do is to make sure that they are sending messages to phone numbers designated to receiving SMS texts.

10) The carrier is experiencing technical difficulties

In some cases, the carrier or sometimes the hardware involved, is having some technical difficulties and messages are not able to be delivered.

We have seen in the course of years all manners of different occurrences, from the servers having a critical error to an accident in construction, resulting in a major data cable being cut.

If your carrier is having problems with their systems, then they should be letting you know what's going on. Look out for updates online regarding outages or repairs from your carrier, and restrict your text messages when this is happening.

Conclusion

There can be quite a few reasons why your SMS message has gone undelivered. In many cases, there isn't much you can do as a sender to help your text messages get through. There are a few things you can do to give your texts the best chance of reaching the recipient.

For example, you can make sure that you're using the correct country codes at the start of your phone numbers. Additionally, ensure you're only sending marketing text messages within the allocated time period of your country, so comply by local rules.

Hopefully, this list better explains delivery problems with SMS messages to help you better understand why your messages may not be delivered.